Apparatus for roasting legumes

ABSTRACT

An apparatus and method for roasting legumes such as soybeans to enhance their nutritional properties. Raw legumes are introduced to a roaster having an oven section and a steeping section downstream of the oven section. The raw legumes are heated to a selected roasting temperature in the oven section as they are moved through the oven section to and through the steeping section. Throughout the passage of the legumes through the oven and steeping sections the legumes are mixed continously.

This invention relates to apparatus and methods for roasting legumes andmore particularly to such apparatus and methods that are especiallyadapted for use in the roasting of soybeans that are to be incorporatedinto cattle feed.

BACKGROUND OF THE INVENTION

It is well known that cattle feed consisting of or including soybeanmeal made from roasted soybeans can increase the amount of proteinescaping degradation (bypass protein) in the rumen of lactating dairycows, thereby enhancing the nutritional value of such cattle feed.However, insufficient roasting of the soybeans results in a dietsupplement which is little or no better than meal produced fromuntreated soybeans, whereas over roasting of the beans does not enhancetheir nutritional value but does result in increased costs resultingfrom the excess roasting time and fuel consumption.

A test procedure has been established to enable the bypass proteincontent in roasted soybeans to be determined. The test results areexpressed in terms of the protein dispersibility index (PDI). A PDI ofbetween 9.0 and 11.0 is achieved when the roasting is optimum.

A principal object of apparatus and methods according to the inventionis to provide for the roasting of soybeans or other legumes in suchmanner as to effect optimum enhancement of the nutritional value or PDIthereof.

SUMMARY OF THE INVENTION

The roasting of soybeans or other legumes according to the inventioncomprises introducing raw soybeans into one end of a cylindrical housingwithin which is a rotatable auger having a helical vane which engagesthe soybeans and moves them from the inlet end of the housing to anoutlet at its opposite end. A substantial portion of the housing isencircled by a heat exchange jacket through which a heating mediumcirculates from and back to a reservoir. The jacket terminates betweenthe opposite ends of the housing, and both the jacket and that portionof the housing which extends beyond the jacket are encircled by thermalinsulating material.

At the outlet end of the housing is a flap which overlies the dischargeend and minimizes the escape of heat therefrom. The flap is formed offlexible material that has good resistance to deterioration by heat andis sufficiently pliable to be displaceable by the beans withoutinterfering with their discharge from the housing.

The auger by means of which the beans are advanced from the inlet end ofthe housing to the discharge end thereof has a helical flight or vanethe diameter of which is sufficiently less than the inside diameter ofthe housing to ensure nonbinding rotation of the auger within thehousing. Between adjacent convolutions of the auger vane arecircumferentially spaced, longitudinally extending mixing blades whichtumble the beans as they traverse the housing and mix them thoroughly soas to obtain substantially uniform heating of each bean.

That part of the housing which is encircled by the heat exchange jacketconstitutes the oven section of the apparatus, whereas that part of thehousing which extends beyond the oven section constitutes the steepingor heat permeation section of the apparatus. In the oven section thebeans are heated to the preselected roasting temperature and mixed sothat virtually all beans are exposed to the roasting heat. In thesteeping section no additional heat is applied, but the roasted beanscontinue to be mixed and thus transfer heat to each other so that eachbean is heated thoroughly throughout and has a temperature whichcorresponds substantially to that of every other bean.

The rate of travel of the beans through the oven and steeping sectionsis so selected that each discharged bean will have been roasted at atemperature and for such length of time as to have the optimum proteindispersibility index.

THE DRAWINGS

Apparatus constructed in accordance with the preferred embodiment of theinvention and for practicing the method according to the invention isdisclosed in the accompanying drawings wherein:

FIG. 1 is a fragmentary side elevational view of the roaster;

FIG. 2 is a fragmentary, longitudinal sectional view of the apparatusshown in FIG. 1;

FIG. 3 is a sectional view taken on the line 3--3 of FIG. 1;

FIG. 4 is an enlarged sectional view taken on the line 4--4 of FIG. 1;and

FIG. 5 is a greatly enlarged view of a portion of the apparatus shown inFIG. 3.

THE PREFERRED EMBODIMENT

A roaster constructed in accordance with the preferred embodiment of theinvention is designated generally by the reference character 1 andcomprises an elongate, cylindrical housing 2 formed of heat transmittingmaterial and having a closure wall 3 at one end. The housing 2 issupported at intervals along its length by (preferably adjustableheight) supporting legs 4 and which are of different lengths so that thehousing occupies a position that is inclined upwardly from its closedend 3 toward its opposite or outlet end. The extent of inclination willdepend upon several factors which will be referred to subsequently.

In communication with the interior of the housing 2 and adjacent theclosed end 3 thereof is an inlet opening 5 having a funnel 6 leadingthereto. The opposite end of the housing 2 is covered by a flap 7 ofpliable material suspended from a bracket 8 which is supported on thehousing 2.

Rotatably accommodated in the housing 2 is a feed or advancing auger 9comprising a shaft 10 journaled at one end in a bearing 11 supported bythe end wall 3 and having a helical flight or vane 12 secured to andextending the length of the shaft 10. The shaft 10 is connected by acoupling 13 to the output shaft 14 of a speed reducing mechanism 15which is driven by an electric motor 16 via a belt 17 trained aroundpulleys 18 and 19. The speed reducer 15 is supported on a shelf 20 andthe motor 16 is supported on a similar shelf 21, both of which aremounted on the end wall 3.

Extending between and secured to adjacent convolutions of the augerflight 12 are mixer blades 22, each of which is identical. Each mixerblade comprises a strut 23 which parallels the shaft 10 and is welded orotherwise suitably fixed to adjacent flights. Each strut is flanked by apair of retainers 24 of springy material. Gripped between the retainers24 is a wiper strip 25 formed of polytetrafluoroethylene (PTFE), theouter end of each strip bearing lightly against the inner surface of thehousing 2. Each strip 25 is maintained in snug engagement with itsassociated strut 23 by means of headed adjusting bolts 26 which extendthrough aligned openings 27 and 28, respectively, in the strut 23 andthe retainers 24. Appropriate force is maintained on the strips 25 byadjustable nuts 29 at the free ends of the bolts 26.

Each mixer blade extends longitudinally of the roaster and parallels theshaft 10. Each wiper also is circumferentially displaced 90° from itsadjacent mixer.

The roaster 1 is divided into two coaxial sections, one of which is anoven section 30 and the other of which is a heat permeating or steepingsection 31 extending in prolongation of the oven section. The ovensection includes a jacket 32 encircling the housing 2 from the inlet endthereof and extending toward, but terminating well short of the outlet.The jacket 32 has a reservoir 33 in which an electrically operatedheating coil 34 of conventional construction is positioned. The coil hasleads 35 and 36 extending externally of the reservoir through a sealedopening 37 for connection to a power source (not shown).

A filler tube 38 communicates with the interior of the jacket andnormally is closed by a plug 39. A drain opening 40 communicates withthe reservoir 33 and normally is closed by a plug 41. The jacket andreservoir 33 form an annular chamber 42 through which heated oil maycirculate, the heat of the oil being transferred through the wall to theinterior of the housing 2. The temperature of the oil may be controlledby an adjustable thermostat 43 in communication with the interior of thereservoir 33 and connected to conventional electrical controls (notshown) contained within a cabinet 44.

The jacket 32 and the chamber 42 extend approximately two-thirds thelength of the housing 2 and define the oven section 30. The remainder ofthe housing 2, i.e., that part which projects beyond the oven section30, constitutes the steeping section 31. Both the oven section 30 andthe steeping section 31 are encircled by thermal insulation 45.

A typical roaster for treating three to four tons of soybeans per dayhas a roaster section of about twenty feet, a steeping section of aboutten feet, and a uniform diameter of about fifteen inches. In any event,the volume of the roaster section preferably is greater than that of thesteeping section.

To condition the apparatus for operation the roaster 1 is located in aposition to receive the soybeans or other legumes that are to betreated. The inclination of the roaster initially is set at an angle ofbetween about 3-5° to the horizontal. Preferably, the supporting legs 4are vertically adjustable so as to enable the inclination of the roasterto be adjusted.

The reservoir 33 and the annular chamber 42 are filled with a fluidheating medium such as oil and such oil then is heated to a desiredtemperature of between about 350-380° F., for example. Preferably, theoil temperature is maintained within about ±2° throughout the process.Although oil is the preferred heating medium, it is possible to use air,steam, or any other suitable medium.

After the temperature of the oven has stabilized at the desired level,fresh legumes are introduced to the oven section of the housing 2 viathe inlet 5 and the feed auger 9 is started and rotates continuously ata speed of between about 45-55 revolutions per hour (rph). As the beansadvance through the oven section 30 from the inlet they are heated bythe heat of the oil that is transmitted through the housing wall 2 andare thoroughly mixed so as to obtain substantially uniform heating ofthe beans.

Following movement of the heated beans from the oven section 30 to thesteeping section 31, the beans continue to be moved by the auger towardthe outlet end of the housing and continue to be mixed by the mixingblades 22. In the steeping section 31 of the roaster no heating orcooling medium is supplied to the beans. However, due to their passagethrough the oven, the beans are at an elevated temperature, therebyenabling all of the beans to become heat permeated. Although no externalheat is applied in the steeping section, it is believed that moisturewill be released from the beans in the form of steam and such steam willassist in delaying the cooling of the beans, thereby assisting inestablishing a substantially uniform temperature throughout each bean.

As the beans approach the discharge end of the roaster they pass athermometer 46 having a stem 47 which projects into the housing 2 and agauge 48 on which a scale is provided. The thermometer enables theroaster operator to determine the temperature of the beans just prior totheir discharge from the roaster. A temperature of between about220-280° F. is acceptable.

As the beans reach the discharge end of the roaster, they will encounterthe flap 7 which, although displaceable from the position shown in FIG.2 to allow beans to exit the roaster, provides a barrier to the escapeof heat from the housing. Consequently, heat is conserved while thebeans become substantially uniformly heated throughout.

Beans that are discharged from the roaster may be collected in asuitable container (not shown) or delivered directly to a conveyor (notshown) and transported to an area for further processing or packaging.

Samples of beans discharged from the roaster may be analyzed todetermine their PDI. If the PDI does not fall within the optimum rangeof 9-11, any one or more of various adjustments may be made to theroaster so as to produce the optimum PDI. For example, the speed ofrotation of the auger 9 may be adjusted, or the temperature of theheating oil may be adjusted, or the inclination of the roaster may beadjusted. The effect of these adjustments should be such as to providesufficient time for the beans to be subjected to an elevated temperatureso that each bean is neither under nor over roasted. A residence time ofbeans within the roaster of 1-1.25 hours and a discharge temperature ofabout 260° F. has produced satisfactory results.

Although the foregoing description has been concerned primarily with theroasting of soybeans, the apparatus may be utilized for the roasting ofother legumes such as peanuts and corn, for example.

This disclosure is representative of a presently preferred embodiment ofthe apparatus and method, but is intended to be illustrative rather thandefinitive thereof. The invention is defined in the claims.

I claim:
 1. Apparatus for roasting legumes comprises a hollow housinghaving a roasting section at one end of which is an inlet; a steepingsection in communication with said roasting section and having at oneend thereof an outlet; means for delivering legumes into said roastingsection via said inlet; means for advancing legumes from said roastingsection to said outlet via said steeping section; means for heating saidroasting section only to a legume roasting temperature; and means formixing heated legumes as they advance from said roasting section to saidoutlet, thereby enabling legumes in said steeping section to transferheat to one another and be discharged from said outlet at asubstantially uniform temperature.
 2. Apparatus according to claim 1including external means thermally insulating said first and secondsections of said housing.
 3. Apparatus according to claim 1 wherein saidadvancing means comprises an auger.
 4. Apparatus according to claim 3wherein said housing is cylindrical and said auger comprises a helicalflight.
 5. Apparatus according to claim 4 wherein said mixing meansincludes at least one mixer member extending between and joined toadjacent convolutions of said flight.
 6. Apparatus according to claim 5including a plurality of said mixer members circumferentially andaxially spaced from one another.
 7. Apparatus according to claim 1wherein said heating means includes a jacket encircling said roastingsection of said housing and a heating medium within said jacket. 8.Apparatus according to claim 7 including a reservoir for said heatingmedium and heating means in said reservoir for heating said medium. 9.Apparatus according to claim 8 including means for adjusting thetemperature of said medium.
 10. Apparatus according to claim 1 includingdisplaceable means at said outlet for minimizing heat loss from saidsteeping section of said housing.
 11. Apparatus according to claim 10wherein said displaceable means is displaceable in response toengagement thereof by legumes.
 12. Apparatus according to claim 1wherein said roasting section of said housing has a volume greater thanthat of said steeping section.
 13. Apparatus according to claim 1wherein said housing is inclined upwardly in a direction from said inlettoward said outlet.